1. Field of the Invention
The present invention relates generally to a mobile ad hoc network. More particularly, the present invention relates to a mobility aware routing technique using a novel link mobility tracking method.
2. Description of the Related Art
Mobile ad hoc networks (MANETs) are self-organizing, rapidly deployable, and require no fixed infrastructure. The MANET is comprised of wireless nodes, which can be deployed anywhere, and must cooperate in order to dynamically establish communications.
The flexibility of a highly dynamic MANET introduces many complexities into the tasks of network control and management, including routing, flow control, and power management, among others. For example, traffic routes change over time, subject to the movement of the mobile nodes. Each mobile node in a MANET acts as a router and moves in an arbitrary direction and speed, hence it is critical to effectively route the traffic to the destination with minimal overhead.
Many routing strategies have been proposed for MANETs that strive towards an optimum tradeoff between efficiency and responsiveness to topological changes. Typical ad hoc routing algorithms, however, tend to become inefficient when the network topology and link availability change frequently, due to the excessive overhead and delay required for re-routing and/or route repair. A key problem with these algorithms is that the routes are chosen based on criteria such as shortest number of hops, yet such routes may not remain available for the duration of a session. When a route failure occurs, a new route must be discovered and a large number of packets may have to be retransmitted. This results in lower network throughput and poorer quality-of-service.
In order to improve the routing performance of MANETs, a node mobility or location prediction concept has been proposed. In the node mobility based routing schemes, each node maintains and periodically checks a list of its neighbor nodes. The number of changes in the list from one sampling instance to the next is taken as a measure of the degree of mobility of the node. During the route discovery phase, the nodes with a high degree of mobility are avoided. The node mobility based routing scheme provides a coarse measure of route stability, but may unfairly penalize relatively stationary nodes that have highly mobile neighbors.
Mobility prediction schemes with a random walk model have been proposed for enhancing the node mobility based routing schemes. While the random walk model is useful for conceptual modeling, the model does not accurately reflect node movements in realistic scenarios. Moreover, estimating the state and parameters of the random walk model cannot be done satisfactorily in real-time.
As another approach, a location history-based mobility prediction scheme has been proposed. In this scheme, the location history of the mobile node is monitored and frequently traveled paths are assigned higher prediction probabilities. However, this scheme requires a large amount of memory to store the set of possible paths and may be cumbersome for mobile nodes.
Also, Global Positioning System (GPS) supported mobility prediction schemes have been proposed. In these schemes, the nodes are geolocated using GPS and their respective velocities are calculated using successive node positions. The node's velocity and position are used to predict the time remaining for the links between nodes to remain active. In the case of nodes with uniform velocities, this prediction scheme will perform well. However, if random changes occur in directions or magnitudes of the node velocities, the prediction will be erroneous.